strip: don't allow empty changegroup in bundle1

Applying an empty changegroup has been an error since the
beginning. The only exception was strip, which would allow to apply an
empty changegroup from the temporary bundle. However, the emptyok=True
option was only set for bundle1 bundles. In other words, temporary
bundle2 bundles would fail if they were empty.

Bundle2 has now been used enough that it seems safe to say that we
simply don't create bundle2 bundles with empty changegroups. That also
suggests that we never create bundle1 bundles with empty changegroups
(i.e. empty bundle1 bundles, since bundle1 is just a changegroup),
because, AFAICT, the code leading up to the application of the bundle
is the same for bundle1 and bundle2.

Therefore, let's stop passing emptyok=True, so we more clearly get the
same behavior for bundle1 and bundle2.

mercurial/repair.py

@@ -213,7 +213,7 b' def strip(ui, repo, nodelist, backup=Tru'
                 txnname = "strip\n%s" % util.hidepassword(tmpbundleurl)
             with repo.transaction(txnname) as tr:
                 bundle2.applybundle(repo, gen, tr, source='strip',
-                                    url=tmpbundleurl, emptyok=True)
+                                    url=tmpbundleurl)
             if not repo.ui.verbose:
                 repo.ui.popbuffer()
             f.close()